With rapid development of electronic and information industries, image capturing devices become essential electronic devices in our daily lives. Image capturing devices are usually used to take photographs or record video data. In addition, image capturing devices are also applied to web cameras for holding a video conference. Recently, the notebook computer is usually equipped with a built-in image capturing device or the desktop computer is connected with an image capturing device.
With increasing development of digital techniques, text documents are gradually created as electronic files. Generally, text documents are scanned by scanning apparatuses and then saved as electronic files such as PDF (Portable Document Format) files. In a case that no scanning apparatus is communicated with the notebook computer, the images of simple documents such as single-sided papers or business cards may be captured by the built-in image capturing device. The images captured by the built-in image capturing device are usually saved as JPEG (Joint Photographic Experts Group) files. Most users prefer using scanning apparatuses to scan the text documents as PDF files because the texts and signs contained in the PDF files are readable by the computer systems and may be converted into editable text files
As known, optical character recognition (OCR) is a process of capturing an image of a document and then extracting the texts from that image. It is possible to analyze images that are captured from the image capturing device according to the OCR technique and saved as JPEG files. As a consequence, individual texts or signs contained in the JPEG files are recognized and converted as editable text files. Since the associated OCR techniques are well established, the image capturing device is gradually adopted to obtain electronic files of the documents.
When an image capturing device is used to capture the image of a document, some difficulties possibly occur. For example, it is critical to hold the document steady. Generally, the focal length of a web camera (image capturing device) of the commercially available computer is set to be approximately 60 centimeters. Such a focal length is suitable to capture the image of the user's facial expression rather than the document. For capturing the image of an article contained in the document by the image capturing device, the document needs to be moved to the focusing position of the image capturing device. If this document is held by the user's hand, the document is readily rocked due to the long holding time. Under this circumstance, the obtained document image is usually blurred. For preventing from rocking of the document and thus obtaining a sharp document image, a static document stand is used for holding the document steady. The use of the document stand and the predetermined focusing position of the image capturing device, however, incur other problems. In a case that the document stand is used in other places, the user should carry the notebook computer and the document stand at the same time, which is very troublesome to the user.
For convenience, the document is directly placed on a working plane (e.g. a desk plane) without the need of the document stand. After the document is placed on a proper location of the working plane, the upper cover of the notebook computer is rotated such that the image capturing device is aligned with or close to the document. Meanwhile, the image of the document may be captured by the image capturing device. When the image capturing device of the notebook computer is used to capture the image of the document placed on the working plane, some drawbacks also occur. The common drawback is occurrence of a distorted image. If the shooting range of the image capturing device is insufficient, the image captured by the image capturing device for a single time is usually incomplete. For solving this drawback, the user usually takes photographs of the document for two times in order to obtain two incomplete images. By means of image processing techniques, these two incomplete images are combined together. In other words, after the upper-half portion of the document is captured by the image capturing device, the document should be moved such that the lens of the image capturing device is aligned with the lower-half portion of the document and the image of the lower-half portion is captured. Since there is no reliable reference tool or reference point on the document, the document is readily aslant during movement of the document. Consequently, the document posterior to movement fails to be parallel with the original location of the document. Under this circumstance, the image of the lower-half portion of the document is distorted and is unsuccessfully combined with the upper-half portion of the document. For obtaining a sharp image, it is necessary to re-capture the document. In other words, the distorted image is troublesome to the user.